Distribution of North American Vivijmridce. 135 



whence come specimens from the Minnesota river, and the 

 Big Sioux river. To the south of Missouri it is replaced by 

 its congener Campeloma coarctation Lea. It has never oc- 

 curred in any stream which is not tributary to the Mississippi 

 or which does not belong to the Mississippi drainage. Its 

 center of distribution appears to be the Mississippi river in 

 that portion of its course which lies between Minneapolis and 

 Keokuk. 



Numerous examples of a much thinner and lighter colored 

 variety come from ponds and lakes all over the area of distri- 

 bution of this species. To these collectors commonly give the 

 name of Campeloma decisum Say. But the less ventricose 

 whorls, elongated peristome, dark olive color, longer spire and 

 heavier texture will serve to differentiate them from Say's 

 form. 



The form described by DeKay as Campeloma integrum has 

 a less wide distribution than either of the forms previously 

 mentioned. Rare specimens have been found in western Con- 

 necticut and Massachusetts. In New York, particularly in 

 the Erie Canal, it is very abundant and large. Thence it 

 ranges westwards to middle Ohio where it assumes such widely 

 diversified characters that a variety name has been established 

 for it. In southern Michigan and western Indiana this species 

 occurs in considerable abundance but nothing like those in 

 which it is found in the New York localities. It has not been 

 reported south of the Ohio river nor south of Pennsylvania. 

 The specimens which have been reported from west of the 

 Mississippi river belong either to Anthony's species or to the 

 variety mentioned below. The limits of distribution of De- 

 Kay's form then will be from western New England to 

 Indiana and Michigan and, so far as we now know, mostly in 

 streams of the Lake drainage. 



Campeloma integrum obesum Lewis, belongs only to the 

 region west of the Appalachians and north of the Ohio river. 

 It came originally from Columbus, Ohio, where it abounds. 

 Specimens have been taken in considerable numbers in Kent 

 county, Michigan. In the Rouge river, Grand river and Reed's 

 Lake, in Michigan the species abounds. West of the Missis- 

 sippi river it has occurred only in one locality, near Iowa City, 

 Iowa, where it exists in very large numbers in a small stream. 

 About Columbus, Ohio, the species appears to be very prolific. 

 Dr. James Lewis, who described this shell, originally based his 

 work on the male shell. Later the female form, with young 

 shells in the ovisacs, fell into his hands ; the great numbers of 

 young coupled with the much more ventricose form of the 

 body whorl caused him to erect a new species which he called 

 Campeloma fecunda. The identity of the two is now estab- 



